The two ways to measure voltage are __________ and __________.

• A. across a component, from a reference
• B. in series with the circuit, across the entire circuit
• C. from a power supply terminal, across a resistor
• D. across a capacitor, across an inductor

Answer: (A)

Voltage is the potential difference between two points, so you measure it by comparing two points with a voltmeter. The two common ways to do this are: across a component, by placing the meter’s leads on the component’s two terminals to read the voltage drop across it; and from a reference point (usually ground) to a node, by connecting one lead to the reference and the other to the node to read that node’s voltage relative to the reference. It’s important to connect the voltmeter in parallel with what you’re measuring so you don’t disturb the circuit; putting it in series would not give a proper voltage reading and would alter the circuit.